It does seem the USA O gauge appeals to the "playing with trains" brigade, rather then the "model railroaders". I agree that most of what I have seen reminds me of when we had tinplate, or Hornby Dublo. Very much at the toy end of the market. I thought Bachmanns foray into ON30 was great and a number of other businesses sprung up to support it with building, conversion kits and the like, but even that seems to have died down somewhat and no new releases in years.
For the UK, the ability to build a workable O gauge micro layout into a 6 foot space with our small rolling stock is what has transformed it and lead to the rise in popularity. Thats not going to happen with a GP and a couple of box cars.